Window and sliding door leaks

Big glass is part of living near the ocean. So are window leaks. Salt, sand and sun wear on frames and seals, and sliders facing the weather take the brunt of storms.

Quick checks you can do

• Weep holes: the small slots at the bottom of the outside frame drain the track. Clear sand and debris with a soft brush or wire.
• Tracks: vacuum sand from slider tracks so water can drain.
• Seals: look for cracked or shrunken glazing seals and weatherstripping.
• Exterior caulk: note gaps between frame and stucco.
• Interior: check for stains or soft drywall below corners.

Common causes

Drying after a window leak

Water often runs down inside the wall. A crew measures the wall below and to each side. If the cavity is wet, baseboard may come off and small holes may be drilled to dry it, or drywall may be removed if it is damaged.

Repair

A window or glazing contractor can reseal or replace components. Leaks from flashing usually mean removing some stucco or trim around the opening. Check any contractor's license with CSLB.

Anatomy of a leak-free opening

A well-installed window or slider relies on layers. The frame itself sheds most water. Weep slots at the bottom drain what gets into the track. Behind the stucco or siding, flashing tape and a sill pan direct any water that gets past the frame back outside. When a leak shows up inside, one of those layers has failed or was never there. Caulk on the outside is the last line of defense, not the first.

Tracing a leak

1. Note exactly where water appears: sill corners, under the frame, or lower on the wall.
2. Check the track and weep slots for sand and debris.
3. Look at exterior caulk joints and stucco cracks around the frame.
4. In dry weather, a controlled water test from the outside, starting low and working up, isolates the entry point.
5. If water appears below the window with no obvious frame leak, suspect flashing or a missing sill pan.

Interior damage to look for

• Swollen or stained window stools and trim.
• Bubbling paint below corners.
• Darkened or cupped floor boards near the opening.
• Musty odor in the wall.

Upgrades that help

When replacing windows, ask about sill pans, proper flashing integration with the weather barrier, and frames rated for the exposure of your site. Have a licensed contractor do the work and check the license with CSLB.

Sliding doors on decks

Sliders that open onto decks or balconies sit at the meeting point of two systems: the door and the deck waterproofing. Water that ponds against the threshold can enter under the door even when the door itself is fine. Make sure the deck slopes away and the threshold sits high enough above the deck surface, and keep drains near the door clear.

When to replace instead of repair

Older aluminum frames with corroded rollers, failed seals and missing flashing are sometimes better replaced than repaired, especially if walls are already open for drying. A window contractor can explain options. Replacement may need a permit; check with the City of Del Mar.

Mold risk after a slow window leak

A window that leaks a little every storm can keep the wall below it damp for months. CDC notes mold grows where there is moisture, including around leaks in windows, and that it grows on drywall, wood and insulation. If you see staining or smell mustiness below a window, a moisture reading can tell whether the cavity is wet. The California Department of Public Health considers visible water damage, damp materials and mold odor signs of increased respiratory risk, especially for children, so do not leave it for the next dry season.

Sources, accessed Oct 16 to 17, 2026: CSLB: Check a license · EPA: Mold cleanup in your home · City of Del Mar · CDC: Mold, basic facts and prevention · California Department of Public Health: Dampness and mold in homes